1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus.
2. Description of the Related Art
In an electrophotographic image forming apparatus, a toner image formed on a surface of an image carrying member is transferred on a belt or on a sheet of recording medium conveyed on the belt. The image carrying member and the belt are arranged to adjacently face each other to form a transfer nip within which the process of image transfer is performed. However, during the process of image transfer, there is a possibility that a small amount of toner in the toner image scatters around thereby deteriorating the image quality. Such a problem is caused by occurrence of an electric discharge between the belt and the image carrying member at an exit of the transfer nip. Because of the electric discharge, the electric polarity of some of the particles in the toner is reversed thereby causing toner scattering.
Japanese Patent Application Laid-open No. 2006-301577 discloses an image forming apparatus in which an electric discharge is prevented from occurring at an exit of a transfer nip formed between an image carrying member and an intermediate transfer belt. For that, a neutralizing electrode is arranged to abut against the inner surface of the intermediate transfer belt at a position within the transfer nip that lies at a downstream side of the direction of movement of the intermediate transfer belt with respect to an abutting portion of an transfer member and the inner surface of the intermediate transfer belt, and on an upstream side of the direction of movement of the intermediate transfer belt with respect to a downstream-side exit of the transfer nip. A voltage of opposite polarity to the polarity of the toner is applied to the transfer member such that the intermediate transfer belt is charged with an electric charge of that opposite polarity. The neutralizing electrode is charged with an electric charge of the same polarity as the polarity of the toner such that the intermediate transfer belt is electrically neutralized. Thus, the difference in the electric potential between the image carrying member and the intermediate transfer belt decreases. As a result, an electric discharge is prevented from occurring at the downstream-side exit of the transfer nip. That prevents toner scattering in the toner image thereby maintaining the image quality.
However, electric neutralization of the intermediate transfer belt at the transfer nip results in poor retention of the toner on the intermediate transfer belt when the toner image passes through the transfer nip. That causes toner scattering even by a slight impact on the intermediate transfer belt thereby deteriorating the image quality.